1. Field of the Invention
The invention relates to a syringe with a hollow needle and a needle holder attached to the hollow needle whereby the needle holder is retractable within the syringe housing and the needle may be retracted with the help of a device into the syringe housing after its use.
2. Description of the Related Art
A syringe of this type has been made known by the state-of-the-art of U.S. Pat. No. 5,480,385. This syringe has the problem that during retraction of the hollow needle, injection solution may be released through the needle and this injection solution might be mixed with the patient""s blood.
A similar syringe has been made known by the state-of-the-art of U.S. Pat. No. 5,114,404. This syringe has the particular disadvantage in that the needle holder, together with the hollow needle, is turned during its release. Parts of tissue may be set free within the patient""s body by turning of the needle, which represents a considerable risk of injury. Furthermore, another syringe was made known by EP-A-0 290 176, which also makes retraction of the needle possible after use. However, this syringe has a problem in that the needle may be in an arbitrary position in relation to its longitudinal orientation. The position of the needle point in relation to the syringe housing is hereby arbitrary and must first be determined before each injection. Retraction of the needle is caused here by means of a pressure spring and there is also the danger that the needle rotates during retraction. Other similar syringes have been made known by WO 92/16 248 and WO 92/058 18.
The above-mentioned disadvantages and problems are avoided by the use of the innovative syringe in that the needle is secured against rotation within the syringe housing in a predetermined position and whereby retraction of the needle in this position is conducted without turning the needle in at least in a portion of the needle path. The portion of the needle path during which the needle remains non-rotating is preferably the foremost portion of the retraction path. The stabilization against needle rotation within the syringe housing makes it possible, for example, to mount the needle always in a predetermined position in relation to a marking on the syringe housing. Since the position of the needle point may be easily seen in the syringe housing, inspection of the needle point is not necessary and injection is thereby made easier and is also safer.
According to the invention, means for volume compensation during retraction of the needle are located in the syringe housing of a typical syringe. These means are designed, for example, in such a manner that a partial vacuum is created before retraction. The fluid displaced during needle retraction then compensates for this low pressure. Thereby it can be prevented that during needle retraction, injection solution is released through the needle, which might be mixed with the patient""s blood.
According to a preferred development of the invention, the means for volume compensation show a movable element placed within the syringe housing, which may be moved before needle retraction to create a partial vacuum. According to further development of the invention, this movable element is at the same time a trigger element by which retraction is caused. This makes a design possible that has very few separate components.
According to further development of the invention, the hollow needle may be moved longitudinally at the circumference and the rear section where it has a seal. Thereby the danger of air injection is prevented by a high degree. At the same time, problems may be avoided during drawing of the injection solution into the syringe and settling of air bubbles is prevented. Since only a seal around the circumference of the needle has to be created, the to-be-sealed area is relatively small and causes a relatively small amount of friction during needle retraction. Additionally, the guiding parts stabilize the needle. According to one version, the syringe is equipped with a Luer nozzle that makes the use of the syringe possible in conjunction with standard hypodermic needles. However, the syringe may also be attached rigidly to a barrel.
According to further development, triggering the retraction is possible at any time whenever the needle retraction is caused by actuating elements, which are located inside the syringe in a radial manner and which move against one another. These actuating elements are preferably attached to the syringe housing. Steady handling of the syringe is achieved by the counter movement of the actuating elements and thereby unnecessary movement of the syringe is avoided.
Additional advantageous characteristics are shown in the related patent claims and the following specifications and drawings.